Hi Lorenzo,
The problem here is that by default on Windows 2003 on 32-bit hardware your 4G of memory is split effectively into 2G halves. 2G for the Windows kernel and 2G of addressable space for the application level.
The OS error 8 you are getting from Windows means it can't allocate the amount of space you asked for.
You can read more about how Windows is handling your 4G of memory in this great article here:
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx
In order to take advantage of more of your physical memory for your processes you will need to add the /3GB option to your boot.ini as described in the above article. This changes the split to 1G for the Windows kernel and 3G for applications.
To take advantage of the extra 1G over the default 2G application space, binaries must have the IMAGE_FILE_LARGE_ADDRESS_AWARE bit set in their image header.
Unfortunately we have not specified the /LARGEADDRESSAWARE linker flag on our Windows binaries at build time which enables this, so even if you did enable the /3GB boot.ini option above, you will still run into an error allocating over that 2G limit with mysqld.exe. It may help you with other applications, though, so I thought I would mention it anyway.
Support for this is something we are looking into enabling as customers more and more frequently want more memory on the Windows OS, but at this stage it is largely untested.
My guess is that various other MySQL buffers and parameters as well as the 1536M innodb_buffer_pool that you are trying to allocate total over 2G, which is why you get the error.
My recommendation is simply to reorganise your MySQL parameters until you get the most out of the 2G possible.
If you really want more than 2G or so per process, it may be time to look at 64-bit or play with the innodb_buffer_pool_awe_mem_mb parameter. (Make sure you have /3GB /PAE in your boot.ini if you do!)
More info:
http://dev.mysql.com/doc/refman/4.1/en/innodb-parameters.html
Hope this helps,
Kind Regards,
Lachlan Mulcahy, Melbourne, Australia
MySQL AB, www.mysql.com
Are you MySQL certified? www.mysql.com/certification